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ASM Handbook, Volume 20: Materials Selection and Design G.E. Dieter, editor, p 96-103

Life-Cycle Engineering and Design ASM International Materials Life-Cycle Analysis Committee*

ENVIRONMENTAL CONSIDERATIONS play an increasingly important role in design and development efforts of many industries. "Cradle to grave" assessments are being used not only by product designers and manufacturers, but also by product users (and environmentalists)to consider the relative merits of various available products and to improve the environmental acceptability of products. Life-cycle engineering is a part-, system-, or process-related tool for the investigation of environmental parameters based on technical and economic measures. This article focuses on lifecycle engineering as a method for evaluating impacts, but it should be noted that similar techniques can be used to analyze the life-cycle costs of products (see the article "Techno-Economic Issues in Materials Selection" in this Volume). Products and services cause different environmental problems during the different stages of their life cycle. Improving the environmentalperformance of products may require that industry implement engineering, process, and material changes. However a positive change in one environmental aspect of a product (such as recyclability) can influence other aspects negatively (such as energy usage). Therefore a methodology is required to assess trade-offs incurred in making changes. This method is called life-cycle analysis or assessment (LCA). Life-cycle analysis aims at identifying improvement possibilities of the environmental behavior of systems under consideration by designers and manufacturers. The whole life cycle of a system has to be considered. Therefore it is necessary to systematically collect and interpret material and energy flows for all relevant main and auxiliary processes (Fig. 1). Life-cycle analysis methods have been developed by governmental, industrial, academic, and environmentalprofessionals in both N orth America and Europe. Technical documents on conducting LCA have been published by the Society of Environmental Toxicology and Chemistry *Thisarticlewas preparedby HansH. Portisch,KruppVDM Austria OmbH (CommitteeChair), with contributionsfrom Steven B. Young,Trent University;John L. Sullivan,Ford Motor Company;Matthias Harsch, Mantled Schuckert, and PeterEyerer,IKP,Universityof Stuttgart;andKonradSanr,PE ProductEngineering.

(SETAC), the U.S. Environmental Protection Agency (EPA), the Canadian Standards Association (CSA), the Society for the Promotion of LCA Development (SPOLD), and various practitioners. For meaningful comparisons of the life-cycle performance of competing and/or evolving product systems, it is important that associated LCAs be conducted consistently, using the same standards. Although the common methodologies developed by SETAC, EPA, CSA, and SPOLD are a step in that direction, a broad-based international standard is needed. Such an effort is being undertaken by ISO 14000 series (TC207). Life-cycle thinking and techniques can be applied to products, processes or systems in various ways: it can help assess life-cycle economic costs (LCAecon), social costs (LCAsoc) or environmental costs (LCAenv). A primary objective of LCA is to provide a total life-cycle "big-picture" view of the interactions of a human activity (manufacturing of a product) with the environment. Other major goals are to provide greater insight into the overall environmental consequences of industrial activities and to provide decision makers with a quantitative assessment of the environmental consequences

of an activity. Such an assessment permits the identification of opportunities for environmental improvement.

Life-Cycle Analysis Process Steps Life-cycle analysis is a four-step process; each of these steps is described in detail below. The process starts with a definition of the goal and scope of the project; because LCAs usually require extensive resources and time, this first step limits the study to a manageable and practical scope. In the following steps of the study, the environmental burdens (including both consumed energy and resources, as well as generated wastes) associated with a particular product or process are quantitatively inventoried, the environmental impacts of those burdens are assessed, and opportunities to reduce the impacts are identified. All aspects of the life cycle of the product are considered, including raw-material extraction from the earth, product manufacture, use, recycling, and disposal. In practice, the four steps of an LCA are usually iterative (Fig. 2).

t\ iii:,o0ii, t,) ,/',,.,ta,,.=I =°.,..,,t0 t) !ir"iL ) "sew" S Disposal

I

Improvement

Fig. 1 Factorsconsideredin the life-cycleengineeringapproach.Source:Ref1

Life-Cycle Engineeringand Design/ 97 Table 1 Example of a life-cycle inventory for an unspecified product Sub~anee Inputs Energy fromfuels,MJ Coal Oil Gas Hydro Nuclear Other Total

Amount

2.75 3.07 11.53 0.46 1.53 0.14 19.48

Energyfromfeedstocks,MJ Coal Oil Gas Other Total feedstock

33.59